1. Field of the Invention
The present invention relates to a device for dumping material onto an underwater bottom or installation, such as a pipeline. The invention also relates to a method for dumping material onto an underwater bottom or installation, as well as to a computer program comprising program instructions adapted to carry out the method.
2. Description of the Prior Art
Flowing media such as oil and gas for instance are typically transported over large distances through pipelines. In order to avoid costly detours, such pipelines may be provided onto the bottom of a sea, which allows to span the shortest distance between two locations. Such pipelines need to be protected adequately and over their entire underwater distance. A useful method to protect pipelines involves dumping (soil) material onto the pipeline, such that the pipeline is actually buried in (soil) material.
A known device for dumping material onto an underwater bottom or installation, such as a pipeline, comprises a vessel, provided with a fall pipe through which the material is dumped on the underwater bottom. The fall pipe is moved along the underwater bottom by the thrust of the vessel. The detailed motion of the fall pipe relative to the underwater bottom is typically controlled by a steering device attached to the lower end of the fall pipe. Such a steering device, also referred to as a Remote Operating Vehicle or ROV in short, is operated manually by vessel personnel.
Dumping materials such as quarry stones for instance at high depths (300 to 600 m are not untypical) and after all also at relatively small depths onto the bottom of the sea involves difficulties such as the influence of currents, movements of the vessel upon violent wind, etc. Since large distances have to covered, it is important to be able to dump the material at the right spot (on top of the pipe line for instance), and also to dump the material efficiently, by which is meant that the desired profile of the underwater bottom has to be reached in as short a time as possible, and by using as little material as possible.
It is an object of the present invention therefore to overcome the drawbacks of the above described prior art device and method, and provide a device and method for dumping material onto an underwater bottom that permits a higher efficiency of operation.